The present invention relates to a ski boot whose upper consists of a variable-volume plastic shell which is closed over the foot and the instep by two superimposed flaps and is provided with at least one tightening device comprising a part secured to the inner side of the shell, that is to say the side corresponding to the inside of the foot, and a part fixed on the outer side of the shell, the outer side of the shell having zones of substantially lower rigidity than the rest of the shell.
Patent FR 2 077 184 proposes the production of ski boots having characteristics as close as possible to a leather boot by using two or more plastics having different mechanical properties. The shell of the boot is formed by successively injecting plastic, with reinforcing elements being introduced at specific points in the injected plastic. The shell obtained is thus a relatively flexible shell provided with reinforcing zones for anchoring the buckles of the boot.
In addition, patent application EP 0 645 101 discloses a ski boot shell having zones of different rigidities and strengths, the strongest and most rigid parts constituting a form of triangular frame whose purpose is to ensure optimum transmission of forces between the leg and the binding.
The object of these designs is to reduce the weight of the boot without weakening the anchoring of the buckles and while ensuring that the boot is still rigid enough to act properly as an interface between the foot and the ski.
The present invention has a different object, namely better support of the foot in the boot and better edge setting.
To this end, the ski boot according to the invention is one wherein said zones of substantially lower rigidity than the rest of the shell lie on either side of a stronger band which extends obliquely from the heel to the front end of the shell and bears one of the parts of the device for tightening the shell.
Since the shell is made of plastic, greater strength will generally be synonymous with greater rigidity.
When the shell is tightened around the foot, the oblique band which lies on the outer side of the shell will press the foot against the inner face of the inner side of the shell while enclosing it, and will pull the foot rearward and press the heel of the foot against the bottom of the shell, but passing between the malleolar region and the region of the metatarsophalangeal joint, which are sensitive zones. The foot is thus kept bearing against rigid parts of the shell, in particular against the shell wall lying on the inner side of the foot, against which the foot will naturally bear when an edge is being set. Since the foot permanently bears against the inner side of the shell, the edges will be set without play, and therefore immediately and more accurately.
The shell is preferably provided with two fastening devices.
The stronger band preferably extends along a curve approximately in the form of an arc of a circle whose center of curvature lies below the boot, and preferably in front of the boot.
Put another way, the stronger band extends along a diagonal which follows the curvature of the boot.
According to one embodiment, the exterior side of the shell has two zones of lower rigidity, on either side of said stonger band, one facing the region of the metatarsophalangeal joint and one lying between the heel and the malleolar region.